The remarkable advance in our knowledge of the organs of internal secretion which has taken place in recent years has brought much light on the parathyroid glands, but still their function and relations to the other organs are very obscure. Their anatomy is by this time fairly well known, particularly to surgeons to whom they have become an object of especial care in operations on the thyroid. Lying, as the parathyroids do, along the posterior margin of the thyroid usually two in number on each side, they may be found as small, flat, soft, yellowish-brown bodies embedded in the loose connective tissue or in the fat or plastered against the thyroid. Generally there is one at the notch of entrance of the inferior thyroid artery and one somewhere else either above or below, sometimes even far down in the fat below the lower pole of the thyroid. They have their